Indicating apparatus for exposure control apparatus

ABSTRACT

Indicating apparatus for use in a camera having a battery and automatic exposure control apparatus is disclosed. The indicating apparatus includes an amplifier and a manually operative switch member which in a first position couples the exposure control apparatus to the amplifier such that the amplifier will energize a low light indicating lamp only when the scene brightness is unsuitable for film exposure. The switch is movable to a second position to connect the first amplifier to a battery by way of a voltage divider network such that the first amplifier will energize the lamp only if a potential of the battery is above a predetermined level.

United States Patent Painton 451 May 23, 1972 [54] INDICATING APPARATUSFOR EXPOSURE CONTROL APPARATUS [72] Inventor: Richard C. Painton, WestWebster, NY.

[73] Assignee: Eastman Kodak Company, Rochester,

[22] Filed: Sept. 10, 1970 [21] Appl.No.: 70,981

[52] US. Cl. ..95/l0 CD, 95/64 D, 352/141 [51] Int. Cl. ..G0lj 1/44,G03b7/08 [58] FieldofSearch ..95/1OC,1OCE,10CT,10CD,

95/53 E, 53 EB, 64 D; 352/141 [56] References Cited UNITED STATESPATENTS 3,397,629 8/1968 Mori et a1. ..95/l0 CT 3,452,656 7/1969 Ruhleet a1. ..95/l0 C 3,518,927 7/1970 Mehlitz et a1 ....95/l0 CE 3,527,1499/1970 Starp et al ..95/10 CI FOREIGN PATENTS OR APPLICATIONS 1,043,4749/1966 Great Britain ..95/ 10 CT 1,093,731 12/1967 Great Britain ..95/l0CT Primary Examiner+Joseph F. Peters, Jr.

Attorney-Robert W. Hampton and Raymond L. Owens ABSTRACT Indicatingapparatus for use in a camera having a battery and automatic exposurecontrol apparatus is disclosed. The indicating apparatus includes anamplifier and a manually operative switch member which in a firstposition couples the exposure control apparatus to the amplifier suchthat the amplifier will energize a low light indicating lamp only whenthe scene brightness is unsuitable for film exposure. The switch ismovable to a second position to connect the first amplifier to a batteryby way of a voltage divider network such that the. first amplifier willenergize the lamp only if a potential of the battery is above apredetermined level.

8 Claims, 2 Drawing Figures Patented May 23, 1972 RICHARD c. PA/NTONINVENTOR.

ATTORNEYS INDICATING APPARATUS FOR EXPOSURE CONTROL APPARATUSCROSS-REFERENCES TO RELATED APPLICATIONS Reference is made to commonlyassigned copending US. patent application Ser. No. 84,389, entitledSelf-Balancing Apparatus for Photographic Cameras, filed Oct. 27, 1970in the name of David L. Babcock and David B. Lederer.

BACKGROUND OF THE INVENTION The present invention relates to apparatusfor indicating if scene brightness is suitable to expose film.

In battery-powered motion picture cameras which also employ circuitryfor indicating if the scene brightness is suitable for film exposure, itis desirable to provide a camera user with convenient means to determinewhether the battery potential is sufficient so that an operator will notwaste film by operating the camera when the battery potential hasdecayed below that potential level necessary for proper operation.

There are prior arrangements employing circuitry for determining ifscene brightness is suitable and for testing the battery potentiallevel. These arrangements are often complex. Moreover, separate anddistinct battery testing arrangements have been used which employvariable deflections of an instrument pointer, which requires operatorjudgement to determine whether the battery potential is suitable forproper use.

SUMMARY OF THE INVENTION In accordance with a preferred embodiment ofthe invention, there is provided an indicating apparatus which iscoupled to an exposure control apparatus having circuitry which developsa signal, when the scene brightness is unsuitable for film exposure. Theindicating apparatus includes a first amplifier which is effective in afirst condition to energize a low light indicating lamp and inv a secondcondition to de-energize the lamp; a second amplifier whichwhen coupledto the first amplifier is responsive to the signal to drive the firstamplifier into the first condition to energize the lamp indicating anunsuitablc scene illumination; a voltage dividing resistance networkadapted to be coupled to the first amplifier and responsive to apotential of the battery being above a predetermined level to cause thefirst amplifier to energize the lamp; and a switch member movablebetween a first position for coupling the first and second amplifiersand in a second position for coupling the voltage dividing network tothe first amplifier.

BRIEF DESCRIPTION OF THE DRAWING The above and other objects andadvantages of the present invention will become apparent from thefollowing detailed description taken in conjunction with the attacheddrawings wherein:

FIG. 1 is a schematic representation showing the general arrangement ofan automatic exposure apparatus, as contemplated by a specificillustrative embodiment of the invention; and

FIG. 2 is a schematic diagram of the indication apparatus represented bya block in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Exposure control apparatusembodying the invention may be employed in cameras of either the stillor motion picture variety. Since such cameras are well known, thepresent description will be directed in particular to elements formingpart of, or cooperating more directly with apparatus in accordance withthe present invention. It will be understood that parts not specificallyshown or described are selectable from those known in the art.

Turning now to FIG. 1, there is shown an exposure control apparatuswhich includes a self-balancing control circuit 9 having a differentialamplifier configuration and indicating apparatus shown fully in FIG. 2and described later in this specification. The circuit 9 is magneticallycoupled to a core winding 17. The magnetic core member 18 is moved in adownward direction when open winding 17 is energized, as subsequentlydescribed, and is moved in an upward direction when close winding 14 isenergized. The core member 18 is mechanically coupled to a diaphragm 21which as shown may take the form of an elongated plate whereby thediaphragm 21 is moved by the magnetic core member 18 in a direction, andto an extent, directly related to the movement of the core 18.

The diaphragm 21 is provided with an aperture 22 through which scenelight passes to a camera or objective lens 23 to a film 24, and anaperture 27 through which scene light passes by way of a lens 28 to aphotosensitive device 41. The photosensitive device 41, such as aphotoresistance element selected from a class in which a parameter, suchas a resistance varies inversely with the intensity level ofillumination instant thereon. The aperture 27 has a generally triangularconfiguration and will be assumed for the purpose of describing theoperation of the system to have a lower tapered portion 27a and an uppertapered portion 27b. The aperture 22 associated with objective lens 23has a triangular or tapered lower portion 22a and a rectangular upperportion 22b.

The exposure control apparatus 10 is adapted to move the diaphragm 21back and forth in accordance with variations in scene brightness tomaintain a selected level of illumination of the photocell. Consideringspecifically the relative shapes of the apertures 22 and 27, therectangular portion 22b of the aperture 22 has a width corresponding tothe maximum light transmitting capability of lens 23. The diaphragm 21is movable through a first range of positions wherein the lower portion27a of aperture 27 and the lower triangular shaped portion 22a ofapertures 22 will be positioned relative to the optical axes of lenses28 and 23, respectively, to vary the effective sizes of the aperturesrelative to both lenses. The diaphragm 21 is movable through a secondpredetermined range of movement wherein the upper tapered portion 27b ofthe aperture 27 and the upper rectangular portion 22b of aperture 22will be disposed in cooperative relation with the lenses 23 and 28,respectively.

In operation, as the intensity of the scene brightness diminishes thediaphragm 22 moves downward and the light transmitted to each of thelenses 23 and 28 will be gradually increased if the diaphragm is in itsfirst range of movement. As the diaphragm 22 moves in its second rangeof movement, the light transmitted to lens 23 will remain constant andcorrespond to the maximum light transmitting capability of the lens 23.As will be later described in more detail, the relative shapes of theapertures 22 and 27, which permits the diaphragm 21 to adjust theeffective size of aperture 27 while maintaining the effective size ofaperture 22 constant in its second range of movement, enables thecontrol circuit to produce a null balance condition during low scenebrightness conditions which are still sufficient for suitable filmexposure to avoid unnecessary operation of a low light indicator lamp 47hereinafter described.

The control circuitry for the apparatus 10 may take various forms knownin the art. The circuit disclosed in commonly assigned U.S. Pat. No.3,427,941 in the name of Lenard M. Metzger is especially suitable foruse with the invention as is the circuit described in commonly assignedcopending US. patent application Ser. No. 823,426 entitled ELECTROMAG-NETIC AUTOMATIC APERTURE CONTROL UTILIZING A VELOCITY SENSING WINDING TOPROVIDE ACTIVE FEEDBACK VISCOUS DAMPING, in the name of Carter et al,now abandoned in favor of application Ser. No. 66,642, filed Aug. 25,1970. Tooperate the circuit, a switch 42 is closed which connects abattery 43 into the control circuit 10. Two NPN transistors 11 and 12are disposed in a differential amplifier configuration which have theiremitter electrodes connected to ground through a common resistance 13.The close winding 14 is connected as a series element in the basecollector circuit of the transistor 11, and the open winding 17 issimilarly connected as a series element in the base collector circuit ofthe transistor 12. The windings 14 and 17 respectively are oppositelywound so that when energized, they will exert opposite forces on themagnetic core member 18 as indicated by the arrows in the drawing.

The differential amplifier is controlled by a resistance bridge havingtwo arms defined by the photocell 41 and resistance element 51respectively and the two arms defined by resistance elements 52 and 53,respectively. The bridge is balanced when illumination incident on thephotocell 41 is such that the ratio or the resistance value ofphotosensitive device 41 to the resistance of element 51 issubstantially equal to the ratio of the resistance values of theelements 52 and 53. ln such condition, equal currents will pass throughdrive coils 14 and 17. Thus, there will be no net force tending to movethe core member 18 which will be in an arrested condition. The system iscalibrated such as by adjustment of the values of resistors 51 and 53 sothat the bridge will be balanced when the amount of light transmitted tothe lens 23 is of the desired magnitude for exposing the film 24. Theselected resistance value of the photosensitive device 41 corresponds toa desired exposure setting.

If the ambient light drops below a previous level where the circuit wasbalanced, the resistance of the photosensitive device 41 will increasethereby increasing the ratio of resistance values of elements 41 and 51to a magnitude greater than that of elements 52 and 53 and cause theamplifier to supply additional energizing current to drive coil 17; thisis effective, in turn, to cause movement of the diaphragm 21 in a down"direction. The open winding 17 will beenergized from a path leading fromthe battery 43, the winding 17, the collector-emitter path of transistor12, and the resistor 13 to ground. This downward movement of diaphragm21 is effective to open apertures 22 and 27, increasing the amount oflight supplied to the photocell 41 and film 24 until a balancedcondition is again reached.

Conversely, under conditions when the amount of light reaching photocell41 and film 24 is greater than the previously established idealmagnitude for good quality pictures, the ratio of the resistance valuesof the elements 41 and 51 will then be less than the ratio of theresistance values of the elements 52 and 53 and the amplifier will thenfunction to supply additional energizing current to drive coil 14 movingthe diaphragm 21 in an upward direction. Movement in this direction willbe effective to close" apertures 22 and 27.

Assuming the diaphragm is in its second range of positions and thecamera lens aperture 22 has increased to a maximum size and balancinghas not yet been reached, the aperture 27 will further increase in sizeuntil balancing is reached or until the upper portion 27b of theaperture 27 is at a size wherein the maximum light transmittingcapability of the lens 28 is reached. In the latter case, the aperture27 can be considered to have reached a maximum size. With the maximumlight transmitting capability of the lens 28 being reached, and withscene brightness further diminishing, the potential difference between aterminal 490 (at the electrical junction between the coil 14 and thecollector of the transistor 11) and a terminal 4912 (at the electricaljunction between the coil 17 and the collector of the transistor 12)will increase until a level is reached whereby the indicating apparatusis activated to provide a conductive path from the battery 43 toenergize the low light lamp 47.

Turning now to FIG. 2, the indicating apparatus 15 is shown coupled tothe exposure control circuit terminals 49a and b and includes a manuallyoperated switch 48, which in the first of two selectable positions,conditions the apparatus 15 to indicate whether the scene illuminationis at a level which has been determined to be too low to permit suitablefilm exposure, and in the second position permits the apparatus 15 todetermine whether the DC potential of the battery 43 is above a selectedlevel.

The terminal 49a is connected to ground by way of a voltage dividingnetwork comprised of resistors 55 and 56. In accordance with theinvention there is provided a second amplifier stage which includes atransistor 50, having its base connected at the junctions of theresistors 55 and 56 and its emitter connected to the terminal 4%. Theswitch 48 is shown in its first position wherein it connects thecollector of the transistor through resistor 57 to the base electrode ofa PNP transistor 60 which is disposed in a first amplifier stage. Thetransistor 60 has its collector electrode connected to ground throughthe low light indicator lamp and its emitter electrode connected to thebattery 43.

During normal operation the voltage difference between the terminals 49aand b will be negligible and the transistor 50 will be in a cut-offcondition. However, when the potential level at the terminal 49a becomespositive with respect to the terminal 49b and reaches a selected leveldetermined by the voltage dividing resistive network and 56, thetransistor 50 will be driven from cut-off into an active mode ofoperation.

Returning momentarily to the time when the transistor 50 wasnonconductive, there would be no substantial voltage difference betweenthe collector base junction of the transistor 60, and the transistorwould also be in a cut-off mode of operation. However, when thetransistor 50 conducts, the transistor 60 will be driven into the activeregion of operation and a substantial current will flow through thecollectoremitter path of the transistor 60 which is sufiicient toenergize the lamp 47 signaling a warning of an unsuitable exposurecondition.

To test the battery potential 43, the switch 48 is moved to its secondposition which open circuits the connection between the collector of thetransistor 50 and the base of the transistor 60, and now disposes thebase of the transistor 60 at the electrical junction of resistors 64 and68 which comprise a voltage including network. The resistance elements64 and 68 are serially connected to the battery 43 and are selected tohave values such that the transistor 60 will conduct when the battery 43has a selected potential level, which is considered necessary forsuitable operation of the exposure control apparatus 10. With such abattery potential level, the transistor 60 will be turned on and driveninto an active condition sufficient to energize the lamp 47.

Reviewing, the low light indicator lamp 47 is not energized immediatelyupon the maximum light transmitting capability of objective lens 23being reached, but is energized only if the ambient light continues todecrease in intensity, and downward movement of diaphragm 11 continuesuntil the scene brightness is at a level which has been determined to beunsuitable for film exposure.

The invention has been described in detail with particular reference toa preferred embodiment thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

I claim:

1. ln exposure control apparatus adapted to receive a battery and havingmeans for producing a signal when scene brightness is unsuitable toeffect desired film exposure, indicating apparatus comprising:

a. electrically operative indicating means;

b. a first amplifier adapted to be coupled to the battery and saidindicating means and being etfective in a first condition for energizingsaid indicating means and in a second condition for de-energizing saidindicating means;

0. a second amplifier adapted to couple the signal producing means tosaid first amplifier and responsive to the signal to produce one of saidconditions in said first amplifier to indicate an unsuitable scenebrightness condition;

d. battery testing means responsive to a potential of the bat tery abovea predetermined level to produce one of said conditions in said firstamplifier and responsive to a potential of the battery below thepredetermined level to produce the other of said conditions in saidfirst amplifier; and

e. a switch member movable between a first position for coupling saidfirst and second amplifiers and a second position for coupling saidbattery testing means to said first amplifier. i

'2. In exposure control apparatus adapted to receive a battery andhaving means for producing a signal when scene brightness is unsuitableto effect desired film exposure, indicating apparatus comprising:

a. electrically operative indicating means;

b. a first amplifier adapted to be coupled to the battery and saidindicating means and being effective in a first condition for energizingsaid indicating means and in a second condition for de-energizingindicating means;

c. a second amplifier adapted to couple the signal producing means tosaid first amplifier and produce said first condition in said firstamplifier in response to the signal to indicate an unsuitable scenebrightness condition;

d. battery testing means adapted to produce said first condition in saidfirst amplifier in response to a potential of the battery being above apredetermined level indicating a suitable potential source level andproduce said second condition in said first amplifier in response to apotential of the battery being below the predetermined level; and

e. a switch movable between a first position for coupling said first andsecond amplifiers and a second position for coupling said batterytesting means to said first amplifier.

3. The invention as set forth in claim 2 wherein said indicating meanscomprises a lamp and wherein said first amplifier includes a firsttransistor which is in an active mode of operation in said firstcondition and a cut-off mode of operation in said second condition.

4. The invention as set forth in claim 3 wherein said second amplifierincludes a second transistor adapted to be coupled to said firsttransistor and responsive to the signal to switch said first transistorto said active mode of operation and wherein said potential responsivemeans includes a voltage dividing network.

5. ln exposure control apparatus adapted to receive a battery, thecombination comprising:

a. photosensitive means having an electrical parameter which varies as afunction of incident illumination;

b. exposure varying means coupled to said photosensitive means andhaving a film exposure aperture, said exposure varying means beingmovable to vary the effective size of said aperture with respect to saidphotosensitive means as a function of said parameter; means coupled tosaid photosensitive means and responsive to a predetermined value ofsaid parameter to produce a signal indicating when scene brightness isunsuitable for film exposure; electrically operative indicating means;

a first amplifier adapted to be coupled to the battery and saidindicating means and being effective in a first condition for energizingsaid indicating means and in a second condition for de-energizing saidindicating means; a second amplifier adapted to couple said signalproducing means to said first amplifier and responsive to the signal toproduce one of said conditions in said first amplifier to indicate anunsuitable scene brightness condition; g. battery testing means adaptedto produce said first condition in said first amplifier in response to apotential of the battery being above a predetermined potential levelindicating a suitable battery potential level and produce said secondcondition in said first amplifier in response to a potential of thebattery being below the predetermined level; and

h. a manually operative member selectively movable between a firstposition for coupling said first and second amplifiers and a secondposition for coupling said battery testing means to said firstamplifier.

6. The invention as set forth in claim 5 wherein said indicating meanscomprises a lamp and wherein said first amplifier includes a firsttransistor which is in an active mode of operation in said firstcondition and a cut-ofi mode of operation in said second condition.

7. The invention as set forth in claim 6 wherein said second amplifierincludes a second transistor adapted to be coupled to said firsttransistor and responsive to t e signal to switch said first transistorto said active mode of operation and wherein said battery testing meansincludes a voltage dividing network.

8. In exposure control apparatus adapted to receive a battery, thecombination comprising:

a. photosensitive means having an electrical parameter which varies as afunction of incident illumination;

b. exposure varying means coupled to said photosensitive means anddefining a film exposure aperture, said exposure varying means beingmovable to varythe efiective size of said aperture with respect to saidphotosensitive means as a function of said parameter;

0. means coupled to said photosensitive means and adapted to produce afirst signal when scene brightness is unsuitable for film exposure and asecond signal when scene brightness is suitable for film exposure;

. an electrically operative lamp;

. a first amplifier adapted to be coupled to the battery and said lampand effective in a first condition for energizing said lamp and in asecond condition for de-energizing said lamp;

f. a second amplifier adapted to couple said signal producing means tosaid first amplifier and responsive to said first signal to produce saidfirst condition in said amplifier energizing said lamp to indicate anunsuitable scene brightness condition and responsive to said secondsignal to produce said second condition in said first amplifierde-energizing said lamp indicating a suitable scene brightness;

g. battery tester means adapted to couple the battery to said firstamplifier and produce said first condition in said first amplifier inresponse to a potential of the battery being above a predeterminedpotential level energizing said lamp indicating a suitable batterypotential level and produce said second condition in said firstamplifier in response to a potential of the battery being below thepredetermined level; and

h. a manually operative switch member movable between a first positionfor coupling said first and second amplifiers and a second position forcoupling said battery testing means to said first amplifier.

1. In exposure control apparatus adapted to receive a battery and having means for producing a signal when scene brightness is unsuitable to effect desired film exposure, indicating apparatus comprising: a. electrically operative indicating means; b. a first amplifier adapted to be coupled to the battery and said indicating means and being effective in a first condition for energizing said indicating means and in a second condition for de-energizing said indicating means; c. a second amplifier adapted to couple the signal producing means to said first amplifier and responsive to the signal to produce one of said conditions in said first amplifier to indicate an unsuitable scene brightness condition; d. battery testing means responsive to a potential of the battery above a predetermined level to produce one of said conditions in said first amplifier and responsive to a potential of the battery below the predetermined level to produce the other of said conditions in said first amplifier; and e. a switch member movable between a first position for coupling said first and second amplifiers and a second position for coupling said battery testing means to said first amplifier.
 2. In exposure control apparatus adapted to receive a battery and having means for producing a signal when scene brightness is unsuitable to effect desired film exposure, indicating apparatus comprising: a. electrically operative indicating means; b. a first amplifier adapted to be coupled to the battery and said indicating means and being effective in a first condition for energizing said indicating means and in a second condition for de-energizing indicating means; c. a second amplifier adapted to couple the signal producing means to said first amplifier and produce said first condition in said first amplifier in response to the signal to indicate an unsuitable scene brightness condition; d. battery testing means adapted to produce said first condition in said first amplifier in response to a potential of the battery being above a predetermined level indicating a suitable potential source level and produce said second condition in said first amplifier in response to a potential of the battery being below the predetermined level; and e. a switch movable between a first position for coupling said first and second amplifiers and a second position for coupling said battery testing means to said first amplifier.
 3. The invention as set forth in claim 2 wherein said indicating means comprises a lamp and wherein said first amplifier includes a first transistor which is in an active mode of operation in said first condition and a cut-off mode of operation in said second condition.
 4. The invention as set forth in claim 3 wherein said second amplifier includes a second transistor adapted to be coupled to said first transistor and responsive to the signal to switch said first transistor to said active mode of operation and wherein said potential responsive means includes a voltage dividing network.
 5. In exposure control apparatus adapted to receive a battery, the combination comprising: a. photosensitive means having an electrical parameter which varies as a function of incident illumination; b. exposure varying means coupled to said photosensitive means and having a film exposure aperture, said exposure varying means being movable to vary the effective size of said aperture with respect to said photosensitive means as a function of said parameter; c. means coupled to said photosensitive means and responsive to a predetermined value of said parameter to produce a signal indicating when scene brightness is unsuitable for film exposure; d. electrically operative indicating means; e. a first amplifier adapted to be coupled to the battery and said indicating means and being effective in a first condition for energizing said indicating means and in a second condition for de-energizing said indicating means; f. a second amplifier adapted to couple said signal producing means to said first amplifier and responsive to the signal to produce one of said conditions in said first amplifier to indicate an unsuitable scene brightness condition; g. battery testing means adapted to produce said first condition in said first amplifier in response to a potential of the battery being above a predetermined potential level indicating a suitable battery potential level and produce said second condition in said first amplifier in response to a potential of the battery being below the predetermined level; and h. a manually operative member selectively movable between a first position for coupling said first and second amplifiers and a second position for coupling said battery testing means to said first amplifier.
 6. The invention as set forth in claim 5 wherein said indicating means comprises a lamp and wherein said first amplifier includes a first transistor which is in an active mode of operation in said first condition and a cut-off mode of operation in said second condition.
 7. The invention as set forth in claim 6 wherein said second amplifier includes a second transistor adapted to be coupled to said first transistor and responsive to the signal to switch said first transistor to said active mode of operation and wherein said battery testing means includes a voltage dividing network.
 8. In exposure control apparatus adapted to receive a battery, the combination comprising: a. photosensitive means having an electrical parameter which varies as a function of incident illumination; b. exposure varying means coupled to said photosensitive means and defining a film exposure aperture, said exposure varying means being movable to vary the effective size of said aperture with respect to said photosensitive means as a function of said parameter; c. means coupled to said photosensitive means and adapted to produce a first signal when scene brightness is unsuitable for film exposure and a second signal when scene brightness is suitable for film exposure; d. an electrically operative lamp; e. a first amplifier adapted to be coupled to the battery and said lamp and effective in a first condition for energizing said lamp and in a second condition for de-energizing said lamp; f. a second amplifier adapted to couple said signal producing means to said first amplifier and responsive to said first signal to produce said first condition in said amplifier energizing said lamp to indicate an unsuitable scene brightness condition and responsive to said second signal to produce said second condition in said first amplifier de-energizing said lamp indicating a suitable scene brightness; g. battery tester means adapted to couple the battery to said first amplifier and produce said first condition in said first amplifier in response to a potential of the battery being above a predetermined potential level energizing said lamp indicating a suitable battery potential level and produce said second condition in said first amplifier in response to a potential of the battery being below the predetermined level; and h. a manually operative switch member movable between a first position for coupling said first and second amplifiers and a second position for coupling said battery testing means to sAid first amplifier. 